It has been heretofore known to apply polyolefin layers to both surfaces of paper prepared for photographic purposes. In many cases, the polyolefin layer which is between the paper support and the light sensitive photographic emulsion has pigments added thereto, such as, titanium dioxide in order to render the polyolefin layer white in appearance. This also increases the reflectivity of the polyolefin surface and improves the quality of the resulting photograph. A problem that exists with such substrates employed in the photographic art is that the sharpness of the resulting image formed in the light sensitive layers is not as high as is desirable when very high quality images are needed, for example, in professional applications. This is generally true because it is not possible to include sufficiently high percentages of pigment material in the polyolefin coatings to achieve the opacity and reflectivity necessary for high sharpness quality images.
In order to overcome this problem, the prior art suggests that a layer of gelatin containing titanium dioxide particles be interposed between one of the polyolefin layers and the light sensitive photographic emulsion. British Patent Specification No. 1,551,258 suggests a photographic paper coated on both sides with polyethylene and coated on one polyethylene surface with a mixture of gelatin, colloidal silica, and particles of titanium dioxide, baryta or (non-colloidal) silica having an average particle size within the range of 0.1 to 5 microns and optionally an anionic surface active agent
U.S. Pat. No. 4,558,002, issued Dec. 10, 1985, teaches a photographic paper having such a structure wherein the layer intermediate to the polyolefin layer and the light sensitive layer is a hydrophilic colloid layer containing a dye or pigment that is not decolored during photographic processing and a white pigment present in the hydrophilic colloid layer in an amount not less than 30% by volume.
U.S. Pat. No. 4,755,454 suggests a structure similar to the two preceding discussed references wherein the hydrophilic colloid layer contains a white pigment present in an amount of at least 68 percent by weight.
In formation of photographic materials, there is a continuing desire for such materials to remain uniform over time both prior to exposure and after exposure and development. It is particularly desirable in photographic papers that photographs remain stable when displayed. In order to accomplish this, there has been a continued desire for more stable colors. There has also been a desire to provide increased stability to present color photographs by treating the supports for the images. Such treatments prevent transmission of gases that would react with colorants. Placing overcoats over the images also prevents transmission of oxygen that would react with the colorants of photographs.
It is disclosed in U.S. Pat. No. 4,861,696 --Tamagawa et al that the wood pulp of a paper may be partially replaced with a synthetic pulp to lower the oxygen permeability. U.S. Pat. No. 3,364,028--Konig discloses prevention of yellow fog formation by coating a baryta layer.
U.S. Pat. No. 4,283,496--Aono et al discloses the formation of a photographic layer having a single layer of polyvinyl alcohol polymer or other polymer that lowers oxygen transmission through said paper.
U.S. Pat. No. 3,582,337--Griggs et al and U.S. Pat. No. 3,582,339 --Martens et al disclose various protective layers for photographic papers.
U.S. Pat. No. 2,358,056 --Clark discloses a photographic paper having a layer of barium sulfate dispersed in polyvinyl alcohol between the photographic emulsion and the paper.
U.S. Pat. No. 3,277,041 --Sieg et al discloses the use of a cross-linked polyvinyl alcohol polymer to increase the water resistance of a photographic paper.
While the life of photographic images has increased, there still remains a need for improvement in stability of photographic images. It is particularly desirable that an increase in the photographic image life be obtained without necessity to reformulate color image couplers which have been balanced for pleasing color rendition and acceptable sensitometric performance. There is also a need for photographic papers that do not exhibit curl.